Method of making cable and cable valley filler



Nov. 1, 1966 F. HlRscH 3,282,040

METHOD 0F MAKING CABLE AND CABLE VALLEY FILLER Original Filed June 15,1964 ATTORNEYS.

United States Patent O l 4 Claims. (Cl. 57-165) This application is adivision of the application filed June 15, 1964, Serial No. 375,235.

This invention relates to improvements in electric cables and moreparticularly to the method of making l-ow voltage cables that have waterrepellent paper fillers in the valleys between insulated conductors andto the method of making the valley lillers.

Multiple conductor electric cables commonly have the valleys between theinsulated conductors filled with paper, jute, or other material toprovide a round contour over which the outer covering or sheath of thecable is applied. It is important, however, to prevent the paper, juteor other filler material from acting as a wick and conveying moisturelongitudinally of the cable. Where paper has been used as the filler ithas been conventional practice to prevent such wick action by using arelatively hard paper which is immersed in wax prior to being twistedinto a filler strand or cord.

Such twisted paper filler strands are hard and have a limiteddeformability, and in order to provide a substantially round contour forthe cable it often is necessary to use a number of them. It has beennecessary to have a number of different sizes of fillers for differentsizes of cables, and for cables having different numbers of conductorsand resulting differences in the shapes and sizes of their valleys.

It is an object of this invention to provide an improved method ofmaking cable of the type having a paper filler in the valleys, and animproved method of making the valley filler for such cable.

Contrary to the usual practice, this invention uses creped paper for thevalley filler instead of kraft paper. Creped paper has been consideredunsuitable for such use in cables where wick action must be avoided. Infact, creped paper has been use in the past as a valley filler only inoil-filled cables where the wick action was desirable, as in theBranthwaite Patent 1,886,786, November 8, 1932, where it is explainedthat with creped paper the oil becomes more quickly distributed throughthe cable. In cables that are filled with insulating oil or other fluidinsulation it is known to provide a channel in the cable to facilitatethe flow of the oil or other fiuid lengthwise through the cable.

The cable with which this invention is concerned involves just theopposite considerations. Travel of moisture or -other liquid, if it getsinto the cable, must be prevented or limited. The valley fillers must beconstructed of material which will not operate with a wick action todistribute moisture lengthwise within the cable. Creped paper cannot beimmersed in wax and then gathered to form valley llers in the way inwhich hard kraft papers are treated because the creped paper will takeup an excessive amount of wax and it is of too low tensile strength tobe formed into a suitable cord or strand for use in a valley of anelectric cable.

This invention involves the novel concept of using creped paper which ismuch lighter, more flexible, and more resilient than ordinary kraftpaper as a valley ller and imparting the necessary water repellentquality to the creped paper by applying wax which is sprayed onto thepaper instead of immersing the paper in Wax. By this method the amountof Wax on the paper is limited and 3282,04@ Patented Nov. 1, 1966 ricethere is no lling of the small crepe valleys of the creped paper withwax. However, the wax sprayed onto the surface of the paper covers theentire surface and after the paper has been gathered and twisted into afiller strand lor cord the wax penetrates the paper and is present insuicient quantity to prevent wick action. It has been found that the waxcan be m-ost easily applied in the necessary small quantity by sprayingit onto the creped paper in the form of a water dispersion before thepaper is folded or gathered. In the preferred embodiment of theinvention the amount of wax applied is approximately three to fourpercent of the weight of the paper with the wax on it, after the waterhas evaporated.

The invention has several important advantages. One is that the crepedpaper had added volume and that a 16 lb. creped paper can be used inplace of 30 to 40 lb. kraft paper fillers which are not creped. Anotheradvantage is that the amount of wax used lon the creped paper is muchless than that used on the kraft paper which has been immersed in a waxbath prior to twisting it int-o a cord or strand. This results in a`substantial saving in material which makes the cable less expensive tomanu facture and which also makes the cable lighter in weight. Forexample, one cable valley filler made in accordance with this inventionweighs 5 lbs. per thousand linear feet as compared with 9.6 lbs. perthousand linear feet for comparable conventional kraft paper valleyfiller.

In addition to the advantages of being less expensive and lighter inweight, the electric cable made in accordance with this inventionactually is better cable. The valley fillers made of the creped paperare soft and more formable than the valley fillers made of the hardkraft paper immersed in a wax bath. Because of this softer and moreformable characteristic the assembly of insulated conductors and valleyllers takes the desired round shape more easily and forms a smoother andbetter final product.

Other objects, features and advantages of the invention willdappear orwill be pointed out as the description procee s.

In the drawings, forming a part hereof, in which like views:

FIGURE l is a diagrammatic View showing a multiconductor electric cablewith the outside sheath removed for part of the length and with theconductors and valley fillers separated to show the various parts of theassembly;

FIGURE 2 is an enlarged sectional view taken on the line 2 2 of FIGUREl; and

FIGURE 3 is a diagrammatic view showing the way in which the fillermaterial is made in accordance with this invention.

In the illustrative embodiment of this invention an electric cableindicated generally by the reference character 10 includes threeelectrical conductors 11, 12 and 13 surrounded by individual walls ofsuitable electrical insulation 15 and enclosed within an outer sheath 17of electrically insulating material. The outer sheath 17 may bemoistureproof or waterproof for use in underground installation. Theinsulated conductors 11, 12 and 13 are located adjacent to one anotherand preferably touch one another along lines of adjacency designated bythe reference characters 21.

There are several valley fillers 23 located in each of the valleysbetween the insulated conductors and outwardly of the lines ofadjacency. These valley fillers 23, originally round or oval in shape,are distorted as necessary to fill the valleys and make the assembly ofthe insulated conductors and the valley fillers substantially circular,so as to fill the space within the sheath 17.

While it is desirable that the valley fillers distort and compress tothe exact cross section of each valley, it is not essential that they llthe valley all the way to the line of adjacency 21 because the fillerspressing against each other and against the sides of insulatedconductors will form a barrier to the entrance of any water into theinterior of the assembly even though they do not reach all t-he way tothe vertex lof the angle formed by the insulated conductors at thepoints lof adjacency. However, it is desirable that the llers shouldreach into the vertex of these angles at frequent locations so as not toleave an unobstructed passage lengthwise of the cable for the trave-1 ofany moisture which may enter at the end of the cable. The actual crosssection of each of the valley fillers 23, in the completed assembly,will vary somewhat at different locations along the length of the cabledepending upon how they are pressed into the valleys and their relationto one another at the time of distortion into the space which they areto till.

The valley llers 23 are originally round or oval in cross section andsince there are limits to which the shape can be distorted it is usualto employ a plurality of fillers in a valley so as to ll the valley withless distortion of the shapes of the individual fillers. Withconventional fillers it has been the practice to employ nine differentsizes of fillers for various valleys on different sizes of cable, butwith this invention it is sufficient to have only three sizes offillers. This saving is because of the `greater softness andcompressibility of the creped paper fillers.

Comparative tests have been conducted on the lightly waxed, creped paperfiller of the present invention and heavily waxed kraft paper llerwidely used in cable manufacture. The following table lists dataobtained using a Randall Stickney gage with a ya in. diameter pressurefoot at room temperature and measuring the deformation l seconds afterthe application of the load:

Creped, .23 x .10.

The above data indicates that the lightly waxed creped paper fillerdeforms 4about twice as much as the more heavily waxed kraft paper ller.

FIGURE 3 is a diagrammatic showing of the way in which one of t-hefillers 23 is manufactured. A strip of creped paper 28, for exampleinches wide is sprayed with a water dispersion of wax from a spraynozzle 30. The dispersion is preferably applied as a ne mist or fog andit is, of course, desirable to apply as little wax as necessary foradequate water repellancy.

An anionic dispersion of parat-'tin wax such as is available from NopcoChemical Company is suitable, for example. The wax itself may be thesame as the wax used in treating kraft paper by the immersion procedure.The temperature at which the dispersion is sprayed onto the crepedypaper -should be such as to prevent the parain from solidifying andseparating. This temperature may be room temperature, but it has beenfound that a temperature of about degrees F. gives very satisfactoryresults. As previously explained, it has been found that wax applied bya fine spray to the surface of the creped paper is in suioient quantityif the weight orf wax is between three and four percent of the weight ofthe combined wax and paper after the water of the dispersion hasevaporated. The dispersion partially penetrates the paper as it issprayed on. This does not leave the paper covered with a continuouscoating of wax and substantial quantities of the interstices of thecreped paper are not filled with Wax. The paper is gathered and twistedwhile wet to form a cord 32, as indicated in FIGURE 3. The amount oftwist may vary, but about six turns per foot gives a satisfactoryproduct. This causes further penetration and distribution of the waxinto the paper and over its surface. The contact between wax coveredareas of the gathers and adjacent areas form barriers which effectivelyclose off against moisture transfer any longitudinally extending openspace-s which may exist within the twisted cord 32.

The creped valley llers of the present invention may be made from 16pound ream weight paper as compared with 30 to 40 pound kraft papersrequired for impregnated fillers. It has been found that valley fillersmade as herein described are adequately water repellant and will notpermit Water to travel along their length by wick action. More wax canbe used, but it is unnecessary and adds both cost and weight. In thecreped paper iiller of this invention the wax comprises 3 to 4% of theweight of the ller, whereas in the wax impregnated kraft paper the waxcomprises 15 to 20% of the weight of the ller. Because of the lowerweight and the greater compressibility of the creped paper filler t-heweight of the ller per foot of cable is substantially reduced, forexample from 9.6 pounds to 5 pounds per y1000 feet in one cable.

This invention may be variously .modified and embodied within the scopeof the subjoined claims.

What is claimed is:

1. The method of making a multi-conductor electric cable which compriseslocating insulated conductors adjacent to one another with valleysbeyond their lines of adjacency, making lightweight water repellantcable valley llers by spraying creped paper with wax to apply a quantityof wax to the surface but limiting the application of wax so as to leaveat least a substantial quantity of the interstices of the creped paperfree of wax, and gathering the paper transversely of its length to thecross section of a cord with a diameter that leaves the gathers looselypacked against one another and the cord capable of distortion andcompression to conform to space within a val- Iley between conductors ofthe electric cable, placing the fillers in valleys between saidconductors, shaping the assembled conductors and llers to a roundedcross section, and enclosing the assembly in an outer sheath.

2. The method described in claim 1 characterized by twisting each paperstrip to confine the gathers to a given diameter.

3. The method described in claim 2 characterized by spraying the wax onthe creped paper in a water dispersion and with the wax approximatelythree to four percent of the weight of the creped paper with the waxthereon after the water has evaporated.

4. The method of making a water repellant, light weight cable valleyfiller which comprises the steps of spraying creped paper with a wax inwater dispersion at a temperature which prevents the wax fromsolidifying and separating, gathering and twisting the papertransversely of its length to a cord, limiting `the application of thewax in water dispersion so as to leave the creped paper with adiscontinuous coating of wax and a substantial quantity of theinterstices of the creped paper unfilled With Wax, and drying the cordto evaporate the water.

(References on following page) 5 6 References Cited bythe Examiner2,388,745 11/ 1945 Katz 57-165 X 2,407,926 9/1946 Hamilton 57-32 XUNITED STATES PATENTS 2,787,045 4/1957 Crawfond 57-165 X 448,174 3/1891Williams et a1 57-154 2,981,052 4/1961 McHenry 57-165X 604,350 5/1898claviez 57-32 5 3,023,267 2/1962 Rubinstein er a1. 174-116 X 1,169,9492/191-6 Gares 174-116 1,837,795 12/19311 schneider 174-116 FRANK J.COHEN, Primary Examiner.

4. THE METHOD OF MAKING A WATER REPELLANT, LIGHT WEIGHT CABLE VALLEYFILLER WHICH COMPRISES THE STEPS OF SPRAYING CREPED PAPER WITH A WAX INWATER DISPERSION AT A TEMPERATURE WHICH PREVENTS THE WAX FROMSOLIDIFYING AND SEPARATING, GATHERING AND TWISTING THE PAPERTRANSVERSELY OF ITS LENGTH TO A CORD, LIMITING THE APPLICATION OF THEWAX IN WATER DISPERSION SO AS TO LEAVE THE CREPED PAPER WITH ADISCONTINUOUS COATING OF WAX AND A SUBSTANTIAL